A conventional supporting frame is assembled by a plurality of joints and supporting rods to become a frame, which can be formed with various configurations. It is known that the joint must be made with different shape for connecting with one rod, two rods, three rods, four rods, five rods, or six rods at a different position in a cubic frame similar to a supporting frame shown in FIG. 7. Since many various joints are necessary for assembling a supporting frame, the manufactured cost will be high and the assembly will be more difficult as well as trouble. Moreover, if one certain joint is lacked, another can not replace it and the supporting frame could not be completed.
In view of the above problems, the primary object of the invention is to provide an improved structure of the joint of a supporting frame to overcome prior known drawbacks. Now the features and advantages of the present invention will be described in detail with reference to the accompanying drawings.